Japanese Patent Laying-Open No. 4-295202 discloses an electric vehicle which is capable of transmitting electric power to and from the external power supply. An electric motor drive and power processing apparatus disclosed in this document includes a secondary battery, inverters IA, IB, induction motors MA, MB, and a control unit. Induction motors MA and MB include Y-connected windings CA and CB, respectively. Windings CA and CB have respective neutral points NA and NB to which an input/output port is connected through an EMI filter.
Inverters IA and IB are provided corresponding to induction motors MA and MB, respectively, and connected to windings CA and CB, respectively. Inverters IA and IB are connected in parallel to the secondary battery.
In this electric motor drive and power processing apparatus, inverters IA and IB can generate regulated sinusoidal AC (Alternating Current) power across neutral points NA and NB and can output the generated AC power to the external device connected to the input/output port. In the recharge mode, the AC power is supplied from a single-phase power supply connected to the input/output port through the EMI filter to neutral points NA and NB of windings CA and CB. Inverters IA and IB converts the AC power supplied to neutral points NA and NB to a DC (Direct Current) power, and charges a DC power supply.
Furthermore, there is a known system which establishes communication between a service station or a charger placed external to an electric vehicle and a control device within the vehicle through an electric power line for charging the vehicle using an external power supply (for example, refer to Japanese Patent Laying-Open No. 7-240705 and Japanese Patent Laying-Open No. 6-245325).
Recently, great attention has been focused on a hybrid vehicle as an environmentally-friendly vehicle. In addition to the conventional engine, the hybrid vehicle uses, as a power source, an electricity storage device such as a battery and a motor which generates a driving force of the vehicle using the electric power from the electricity storage device.
If this hybrid vehicle is also capable of transmitting the electric power to and from outside the vehicle, the hybrid vehicle can be used as power supply equipment by supplying electric power from the vehicle to a load external to the vehicle while generating electric power using the engine, and the electric power generation with the engine can be suppressed by charging the battery from an external power supply.
If the hybrid vehicle capable of transmitting the electric power to and from outside the vehicle can establish communication with the apparatus external to the vehicle through an electric power line for transmitting the electric power to and from outside the vehicle, various pieces of information can be exchanged between the hybrid vehicle and the apparatus external to the vehicle without additionally providing a communication cable.
During the electric power generation using the engine, however, voltage noise may occur due to the electric power generation to thereby cause distortion in the waveform of the voltage transmitted through the electric power line. If the communication is established through the electric power line while distortion occurs in the voltage waveform of the electric power line, the probability of a communication error increases, which may interfere with the normal communication.